Mechanosensitive sensory hair cells are the linchpin of our senses of hearing and balance. Our inner ear harbors about 15,000 cochlear and about the same number of vestibular sensory hair cells, which are the mechanoreceptors of our senses of hearing and balance. Because of their paucity, molecular studies on hair cells have been limited, and, consequently the molecular basis of their function is unknown. Aside from being scarce, hair cells are also sensitive to mechanical and chemical insults. Acoustical overstimulation, chemotherapy, aminoglycoside drug side effects, the effects of aging, and increasingly noisy environments contribute to the deterioration of hearing over time. As a result, hundreds of millions of patients worldwide are permanently debilitated by hearing loss and balance problems. The main reason for the permanence of these chronic disorders is the fact that mammalian cochlear hair cells do not spontaneously regenerate and that the limited regeneration observed in the vestibular system is inadequate to restore function. Protocols to generate inner ear sensory hair cells and supporting cells in vitro would find great use as a platform for testing compounds with respect to ototoxicity, otoprotection, and otoregeneration. The present invention addresses these issues.